WO2007022862A2

WO2007022862A2 - Method for the production of a multilayer electrostatic lens array

Info

Publication number: WO2007022862A2
Application number: PCT/EP2006/007780
Authority: WO
Inventors: Dagmar Gerthsen; Fabian Perez-Willard; Katrin Schultheiss
Original assignee: Universität Karlsruhe
Priority date: 2005-08-24
Filing date: 2006-08-05
Publication date: 2007-03-01
Also published as: DE102005040267B4; US20100065741A1; WO2007022862A3; US8487268B2; DE102005040267A1; JP2009506485A; EP1920453A2

Abstract

The invention relates to a method for producing a multilayer electrostatic lens array comprising at least one lens electrode, particularly a method for producing a phase plate, as well as said lens array, said phase plate, and a transmission electron microscope encompassing said phase plate. The lens array or the phase plate is produced from a thin unsupported silicon nitride membrane that is mounted into a macroscopic chip while additional layers are deposited. The central bore and the aperture opening are milled out by means of an ion beam.

Description

Method for producing a multilayer electrostatic lens assembly

description

Field of the invention

The invention relates to a method for producing a multilayer electrostatic lens assembly having at least one lens electrode in general, a method for producing a phase plate in particular, and the lens assembly, the phase plate and a transmission electron microscope with the phase plate.

Background of the invention

The present invention arose from the need to produce a so-called Boersch phase plate. However, the method developed by the inventors can also be used to make other multilayer electrostatic lens assemblies.

A commonly used method for studying the structure of, for example, biological medical objects is transmission electron microscopy (TEM), which can achieve a resolution in the range of less than 1 nm. In this way, structural details of an object in the range of nearly atomic dimensions can be mapped. However, biological objects consist mainly of light elements such as carbon, hydrogen and

Oxygen, so that the high-energy electrons that are used for the imaging, almost not absorbed become. For this reason, there is no exploitable amplitude contrast, so that the object in the image remains invisible in an amplitude contrast measurement.

However, the phase of the electrons is slightly shifted. One therefore calls objects with this property as phase objects. They can therefore be visualized with a phase-contrast electron microscope. To produce the highest possible phase contrast, the phase of the non-scattered phase objects is

Electrons (zero-beam electrons) shifted by about 90 °, in order to obtain a maximum phase contrast with subsequent superposition of the phase-shifted non-scattered electrons with the scattered electrons in an interference image. The phase shift of the zero beam can be realized in principle by a phase plate.

In light microscopy, the use of a phase plate for phase contrast microscopy is already realized in practice. For this purpose, a so-called Zernicke

Phase plate in the form of a λ / 4 plate used in the rear focal plane of the lens.

One known method for a TEM works with the generation of phase contrast without phase plate. It is necessary to defocus the image in order to obtain structural information about the object. In order to cover the widest possible range of spatial frequencies, so-called defocus series (several images with different defocusing) are recorded. This is very cumbersome and tedious. To make matters worse when recording image series that the samples are often sensitive to radiation and only with a small electron dose without significant radiation damage can be charged. For this reason, the signal-to-noise ratio in the images of a defocus series is usually low. Therefore, the image quality is much in need of improvement. However, to the knowledge of the inventors, this method represents the only actually practicable method for phase-contrast electron microscopy.

Another to the knowledge of the inventors, however, so far still more or less theoretical solution for the production of

Phase contrast is due to the use of a phase plate for a TEM that produces the desired phase shift of typically 90 ° between scattered and non-scattered electrons in the back focal plane of the transmission electron microscope objective lens.

The technical realization of a phase plate for a TEM, however, is extremely difficult, due to the extremely small wavelength of the electrons in the order of 10 ^{~ 12} m compared to the wavelength of visible light

(4 ... 7 x 10 ^"7 m).

A research-stage embodiment provides for a thin carbon film, which in the rear

Focal plane of the microscope objective is positioned. In the carbon film is located in the middle of a small hole with a diameter of about 1 micron, through which the beam of non-scattered electrons passes. On the other hand, the scattered electrons pass through the carbon film and, due to the internal potential of the carbon, experience an additional phase shift in relation to the non-scattered electrons. Such a phase plate is also referred to as a Zernicke phase plate. The However, use of such a Zernicke phase plate has hitherto proved impractical due to the following difficulties.

Due to the inelastic scattering of the electrons in the carbon film, the electron coherence is partially lost. Furthermore, the granularity of the carbon film leads to spatial variations in the phase shift. In addition, the carbon film is damaged by the high-energy electrons. The spatially inhomogeneous contamination of the carbon film associated with the small thickness of about 3 x 10 ^-8 m results in charges and uncontrollable phase shifts, and the phase shift can only be controlled by the thickness of the film The plate can be extensively removed and replaced by a new plate, in principle no adjustment of the phase shift is possible without replacing the plate.

For these reasons, the use of a Zernicke phase plate for a TEM has proven impractical.

Recently, Lentzen in Ultramicroscopy 99, 211 (2004) proposed using a double hexapol

Aberration corrector in the imaging system of a TEMs to realize a Zernicke phase plate. However, the proposed structure is complex and extremely expensive.

A considerably better variant for a phase plate according to the inventors is the so-called Boersch phase plate. Although it was already published in 1947 by Hans Boersch in "On the Contrasts of Atoms in the Electron Microscope", Z. Naturforschung, 2a, 615-633, 1947 proposed; the actual production of a Boersch phase plate, however, according to the current state of knowledge of the inventors has not succeeded to this day. The extraordinary difficulty lies in the small dimension of the phase plate and its nevertheless complex structure. Therefore, only more or less theoretical approaches from EP 0 782 170 A2 and WO 03/068399 are known so far. For a better understanding, the basics of a phase-contrast microscope are first described.

The principle of phase-contrast electron microscopy is shown in FIG. In a transmission electron microscope 1, an electron source 2 generates a high energy electron beam 4 which is collimated by a first and second condenser lens 5, 6 to scan the sample 8 after an upper objective lens 7. The scattered and non-scattered electrons are focused by an objective lens 9 and pass through the phase plate 20 in the back focal plane of the objective lens 9.

The zero beam 10, that is, the non-scattered electrons, are passed through an electric field 12 generated by a ring electrode 14. By the electric field 12, the zero-beam electrons 10 experience a phase shift compared to the scattered electrons 16, which do not undergo the electric field.

After a first intermediate image 17, the electrons pass through an intermediate lens 18 and a

Projection lens system 19 to produce an image 22 of the sample, for example on a film or a CCD chip 24. In EP 0 782 170 A2 a proposal is now made for a phase plate for a phase-contrast electron microscope. For the intended production, a substructure made of a silicon substrate which is coated on both sides with etch-resistant layers is used. However, this layer arrangement is merely an auxiliary carrier and not part of the phase plate to be produced (see Fig. 6a to βe in EP 0 782 170 A2). The structure of the phase plate is carried out by depositing of insulating and metallic layers and etching. Finally, however, the silicon substrate with the etching-resistant layers must be completely removed by etching from the highly sensitive phase plate in a two-step process. How this should be done in detail, about the EP 0 782 170 A2 is silent. The rest remains

Production in many respects unclear. In any case, the process is complicated by a variety of deposition and etching steps as well as the removal of the auxiliary substrate. In addition, there is a high probability that the highly sensitive phase plate is destroyed when the auxiliary substrate is removed. Therefore, the method appears to be at least impractical. In any case, an actual realization is not known.

In addition, FIGS. 6a to 6e and the description on page 7, lines 4 to 35 in EP 0 782 170 A2, only show the production of the central electrode of the phase plate. However, this must be suspended by a Boersch phase plate in an aperture stop. How this should be done, makes the EP 0 782 170 A2 no information, so that from this no complete teaching for the preparation of a Boersch- phase plate can be removed. Furthermore, WO 03/068399 describes a phase plate for electron microscopy. In this document, however, it is about the non-mirror-symmetrical arrangement of the carrier of the ring electrode. This particular geometry is described as advantageous for reconstructing image information using Friedel symmetry. This phase plate consists of an annular electrode with an inner diameter of about 1 micron, through which the zero beam is passed. The ring electrode is over to

Example three bars attached to a bracket. Apart from some preferred forms of support means formed by the supports (see Figures 1-3 of WO 03/068399), the document does not indicate its own manufacturing process. Reference is made to EP 0 782 170 for the details of the construction of the phase plate. Therefore, the above-described disadvantages and problems are the same.

Although the Boersch phase plate already in 1947 by Hans

Boersch has been proposed, even with the inclusion of the teachings of EP 0 782 170 and WO 03/068399 so far no actually prepared Boersch phase plate is known. This is the inventors with the proposed manufacturing method proposed to the best of our knowledge now succeeded for the first time.

General description of the invention

Accordingly, it is an object of the invention to provide an actually feasible manufacturing process for a Boersch phase plate.

Another object of the invention is to provide a versatile and improved process for producing micro or nano-lenses in general. Yet another object of the invention is to provide a simple, cost-effective, production-ready method for producing a micro or nano-lens arrangement, in particular a Boersch phase plate with high yield.

Yet another object of the invention is to provide a manageable, stable, high quality and low cost micro or nano-lens array or Boersch phase plate.

The object of the invention is solved by the subject matter of the independent claims. Preferred embodiments of the invention are defined in the dependent claims.

According to the invention, a method is proposed for producing a multilayer electrostatic micro-lens arrangement in which at least one lens electrode is electrically shielded on both sides by means of shielding layers in order to produce an electric lens array in an inner opening of the lens electrode. The method comprises the following steps:

a) Provide a manageable stable

Holding chips, which is substantially larger and thicker than the lens assembly to be produced and which has at least one thinned membrane window with a respect to the substrate material of the chip considerably thinned but still self-supporting membrane of a first membrane material, wherein the membrane or original membrane, in particular integrally with the chip is clamped in the membrane window and wherein the membrane represents a first layer of the lens assembly to be produced. In other words, the membrane at the same time part of the robust and easy to handle chips or wafers and preferably forms its front-side planar surface. Preferably, the membrane is a thin film or film produced on the front side prior to backside thinning of the chip on the chip, and significantly thinner than the macroscopic support chip.

b) applying a second layer of a coating material on a first side of the membrane, wherein either the membrane or chip material, an electrically insulating material and the

Coating material is an electrically conductive material or the membrane or chip material is an electrically conductive material and the coating material is an electrically insulating material, so that an at least two-layered membrane clamped in the window of the chip consists of an electrically insulating first insulation layer and an electrically conductive first shielding layer , The second layer is preferably applied by known PVD or CVD techniques. However, galvanic or electron or ion beam assisted deposition also appears possible. For example, In the case of an insulator original membrane, a metal layer is evaporated or in the case of a metal foil as the original membrane

Insulator layer deposited. In this case, preferably the first insulating layer on the front side and the metal layer are arranged on the back side.

Particularly suitable is an original membrane of silicon nitride has been found. The original membrane preferably has a thickness of less than 5 μm, preferably between 30 nm and 1 μm. However, layer thicknesses down to 20 nm or even 10 nm are possible. The self-supporting membrane area within the window is preferably between about 10 × 10 μm ² and a few cm ² , preferably between 20 × 20 μm ² and 5 × 5 mm ² . Particular preference is given to membrane thicknesses of 50 nm to 200 nm and membrane sizes of between 50 × 50 μm ² and 500 × 500 μm ² . The membrane may be square or have another nearly any two-dimensional geometric shape. Depending on the membrane size, a wafer can have multiple membranes and / or multiple lenses or phase plates can be made in a membrane.

The silicon nitride membrane advantageously has a surface which is sufficiently smooth for the subsequent spin-coating of the lithographic lacquer, in particular on the front side. The self-supporting membrane was produced as follows. A crystalline silicon wafer or chip is first polished. On the polished side, a silicon nitride layer is deposited by means of CVD. Preferably, this is a silicon-enriched silicon nitride layer (Si _{3 + X} N ₄ _ _x ), which has a lower internal stress than stoichiometric silicon nitride. Due to the smaller lattice mismatch, the silicon-enriched silicon nitride layer (Si _{3 + X} N ₄ _× ) on silicon grows considerably less stress on silicon than a stoichiometric silicon nitride layer (Si ₃ N ₄ ). Nevertheless, a (reduced) internal stress remains. This internal stress is also present in the self-supporting membranes used. However, in self-supporting membranes of silicon-enriched silicon nitride, larger parts can be milled out than in the stoichiometric case, without jeopardizing the integrity of the membrane. This is particularly advantageous if non-circular symmetric parts are to be removed from the membrane. For example, the aperture opening of the Boersch phase plate is only approximately circularly symmetrical. Subsequently, the silicon chip is photolithographically patterned from the opposite side and wet-etched to the silicon nitride layer, which remains as a self-supporting membrane in the window.

Alternatively, SiO ₂ , Al ₂ O ₃ , MgFl ₂ , niobium oxide, carbides or metal oxides can generally be used as the membrane material. The frame-like macroscopic chip around the membrane window preferably has a thickness of 100 μm to a few mm and a size of, for example, 1 cm ² , ie the membrane is at least one or more orders of magnitude thinner than the frame area of the chip.

c) generating an electrode and a lead made of electrically conductive material on the, the electrically conductive layer opposite side of the electrically insulating layer of the membrane. Preferably, the outer shape of the electrode is substantially circular and the lead is elongated with a width approximately that of

Electrode or narrower. For this purpose, a metal layer is preferably deposited as the electrode layer, in particular vapor-deposited and structured by means of a lift-off technique. During lift-off, an imageable lacquer is first spin-coated onto the insulating layer of the membrane, in particular its flat front side (so-called spin coating), and subsequently exposed, structured, vapor-deposited and detached. These methods are known in principle to the person skilled in the art. In principle, photo or electron beam lithographic processes with appropriate coating can be used. For the very fine electrode and the lead, however, electron beam lithography has proven to be particularly suitable. As an alternative to the lift-off method, it is also possible to carry out structured deposition of the electrode and supply line by means of ion or electron beam assisted CVD. In particular, alternative non-spherical shapes for the electrode are possible.

d) applying an electrically insulating second insulation layer at least on the electrode and the lead and the first insulation layer located around the electrode so that at least the electrode, in particular completely and the lead are covered by the second insulation layer, wherein the electrode and at least partially Lead between the first and second insulating layer with a preferred thickness of 10 nm to 1000 nm, more preferably 50 nm to 250 nm are included to be electrically isolated.

e) applying an electrically conductive second shielding layer on the opposite side of the electrode of the second insulating layer, so that in the membrane window a self-supporting sandwich-like layer arrangement is formed, which comprises in the region of the electrode and the lead at least the five following layers in the following order: the first Shielding layer, the first insulating layer, the electrode layer, the second insulating layer and the second shielding layer. Outside the electrode and the lead, the layer assembly preferably has at least the four following layers in the following order: the first shielding layer, the first insulating layer, the second insulating layer, and the second shielding layer. In particular, the sandwich-like layer arrangement is self-supporting and not applied to an auxiliary substrate, which must be subsequently removed. f) subsequent to steps a) to e), the entire sandwich-like layer arrangement, ie the five layers which make up the lens arrangement to be produced, is pierced in the area of the electrode. The layer arrangement is self-supporting in the step of piercing, so that no auxiliary substrate is needed to support the membrane. Accordingly, in the method according to the invention, therefore, the original membrane remains as one of the layers of the layer arrangement to be produced. This circumstance is advantageous because etching away an auxiliary substrate can lead to the destruction of the device.

By means of the complete piercing of the layer arrangement, the continuous inner opening in the electrode is produced, so that the ring shape of the electrode is formed and the layers of the lens arrangement are exposed to the bore. The diameter of the bore is preferably from 10 nm to 100 .mu.m, preferably 100 nm to 10 .mu.m, more preferably 500 nm to 4 microns.

The continuous drilling through the five layers is preferably carried out by means of micro- or nano-lawns. For this purpose, a device with which a focused ion beam can be generated and controlled is particularly suitable (so-called "focused ion beam device" or "focused ion beam device"). The layered material is sputtered away locally by means of the focused ion beam, so that the bore is cut out. This method advantageously allows a very precise cutting and avoids short circuits between the layers. The minimum achievable diameter of the bore depends on the diameter of the ion beam and the thickness of the layer arrangement. Furthermore, can be next to circular Geometries also produce other lens shapes such as quadrupole octupole or Hexapolsymmetrien.

In particular, step a) takes place at least before steps b) to f). Unless expressly defined, no limitation on the order shall be defined otherwise by the designation of the steps with letters. For example, Step b) can take place before or after step c).

With the production of the bore, the production of the lens in a chip with a membrane window is preferably completed. When using multi-membrane wafers, the wafer can subsequently be divided into individual chips, preferably with one or more membrane windows (n) each. It is advantageous, in particular in a TEM, to use a chip with several, possibly even different lens arrangements or phase plates, since these can then be exchanged in an advantageous manner without breaking the vacuum. Also, a chip may additionally contain free windows.

As the first and / or second shielding layer, a noble metal, e.g. Gold, platinum or silver with a thickness of preferably 100 nm to 200 nm vapor-deposited. However, layer thicknesses of the metal layers are possible down to 50 nm or less. In principle, even layer thicknesses between 10 nm and 5 microns are possible.

In the embodiment described above, the method according to the invention can already be used for the production of solid, ie flat closed but very thin lens arrangements. Advantageously, the invention generally enables the production of multilayer lens arrangements having a total thickness of in particular less than 1 μm and lateral dimensions in the range in particular of a few μm to a few hundred μm or even smaller. These are of considerable interest in the field of nanotechnology, among others. The lens arrangements are particularly suitable for electron optics and are advantageously by selecting the size and / or lens thickness to the desired spatial extent of the electric field, by selecting the insulator layer thicknesses (dielectric strength) to the desired field strength and choice of shape to the distribution of field strength diverse customizable.

A particular application of the method according to the invention, however, opens up with the production of a Boersch phase plate for an electron microscope, according to a particular embodiment of the invention. Apart from the theoretical approaches acknowledged in the introduction, the inventors are not aware of an actually feasible method for producing a Boersch phase plate. In each

Case is the presently proposed method as well as the result of considerably advantageous simplicity but also precision.

The Boersch phase plate according to the invention has a frame-like aperture stop, which defines an inner aperture for scattered electrons in the electron microscope, wherein within the aperture opening a shielded lens with a lens or ring electrode by means of at least one narrow

Suspension member which radially spans the aperture opening is suspended on the aperture stop. For this purpose, first a chip with a membrane is used, which has at least the size of the aperture diaphragm. The diameter of the phase plate or aperture is eg about 50 μm. Depending on the requirement, however, 5 μm up to a few hundred μm are also possible.

In addition to the steps described above, the aperture opening is generated in a step g). In this case, step g) subsequently takes place at least steps a) and at least part of c) (eg after the coating), preferably below a), b) and c) and / or before the steps d), e) and / or f). The most preferred order of steps is a), b), c), g), d), e), f).

The aperture opening is preferably cut out or milled out of the layer arrangement by means of an ion beam. In particular, the same "focused ion beam device" is used as later for milling out the bore, however, a dry etch, such as reactive ion etching, could be used.

When milling out (sputtering of the thin layers) is allowed from the membrane a central electrode support area around the electrode and at least one or more connecting webs, such that the electrode support region suspended by means of the or the connecting webs on the aperture inside the aperture, preferably cantilever in the center of the aperture is.

Since the Boersch phase plate is extremely small, high demands are placed on the precision of the

Positioning during milling provided. For this purpose, it has proven to be advantageous to produce one or more position markings, so-called "alignment marks" on the layer arrangement, prior to milling the aperture opening, which may be useful in the same step as the electrode and the supply line can be generated or patterned deposited. This could actually one

Position accuracy can be achieved relative to the electrode of about 100 nm.

Preferably, in step b), the second layer is applied at least over the entire area of the aperture stop or membrane in order to be able to reach also in the region of the connecting webs, i. also the supply line, which (later) runs on one of the connecting webs to produce a shielded cable. In particular, in step c) the supply line is generated as extending from the electrode to at least the edge region of the aperture stop. In particular, the connecting web has a slightly greater width than the feed line and the electrode carrier region has a larger diameter than the electrode, so that the feed line and the electrode are framed in a plan view of the chip material. This results in the deposition of the second insulating layer according to step d) a closed electrostatic insulating jacket around the electrode and the lead from the two insulating layers. The second insulation layer is preferably applied only after the aperture opening has been produced, since the layer arrangement to be cut through is thinner and the alignment marks are more clearly recognizable.

The steps d) to g) are preferably in the following

Sequence performed: generating the aperture opening according to step g) with a positioning with the aid of the alignment

Marks, subsequently applying the second

Insulation layer according to step d), subsequently applying the second Shielding layer on the second insulating layer according to step e), subsequently piercing the five layers of the lens according to step f).

Thus, the finished phase plate has a ring electrode with a central opening, an electrical lead, two insulating layers and two shielding layers.

Preferably, the first and second insulating layers together form an outwardly closed electrically insulating jacket around the ring electrode and the lead, the jacket extending annularly around the ring electrode and extending along the tie bar at least to the outer edge of the aperture opening.

According to a preferred embodiment of the method according to the invention, the phase plate during the application of the second electrically conductive

Shielding layer tilted in several directions to coat the lateral end faces of the electrode support portion and the connecting webs or with the electrically conductive material of the second shielding layer, wherein an electrical contact between the first and second shielding layer is made. As a result, the first and second shielding layers form a closed electrically conductive shielding cage around the electrode, the shielding cage being electrically insulated from the electrode by means of the first and second insulating layers or cladding. In this case, the conductive cage extends annularly around the casing and also extends along the connecting web at least to the outer edge of the aperture opening. In other words, the suspension elements are also in the Essentially completely encased with a conductive layer to effectively shield the electric field in the outer region of the ring electrode or to prevent charging. However, within the bore, more specifically at its outer periphery, the five layers a) to e) are exposed to create the electric lens field in the area of the bore.

Thereby, the electric field is confined to the inside of the electrode and completely shielded to the outside as far as possible, so that the phase of the scattered electrons is not affected. These are transmitted in the field-free areas between the connecting webs or support elements.

The subject of the invention is therefore also the inventively producible lens arrangement or Boersch phase plate, as well as a phase contrast transmission electron microscope with built in a focal plane of the microscope Boersch phase plate, the zero beam are passed through the ring electrode and the scattered electrons substantially through the aperture opening.

Thus, the phase plate produced according to the invention differs structurally from those made by means of an auxiliary substrate, at least one of the layers of the lens, the first suspension element and the outer frame of the aperture diaphragm, namely the original membrane, being simply continuous or integral of one and the same worked self-supporting surface applied to the chip membrane layer. Preferably, the original membrane is realized as the first insulating layer of the lens arrangement and made of silicon nitride. The remaining layers applied in steps b) to e), ie the first shielding layer, the second shielding layer, the electrode layer and / or the second insulating layer are deposited on the membrane or deposited, in particular by means of PVD or CVD deposited layers.

The feed line preferably comprises an elongated connecting portion which extends radially on the first connecting web from the ring electrode to the chip and on the front side in a

Contacting field opens, which by means of conventional techniques and macroscopic contact elements, e.g. Contact pins can be contacted in order to be able to apply a voltage to the ring electrode by means of a voltage source connected to the contacting field. For this purpose, the contacting field in the tangential direction has a greater extent than the supply line. Preferably, the ring electrode, the lead and the contacting field are integrally formed. The distance between contacting field and ring electrode can be varied within wide ranges.

More preferably, the suspension elements spanning the aperture opening are sandwiched. The first suspension element in which the supply line runs has therefore, in particular in this order, at least the layers a), b), c), d) and e) and the other suspension elements the layers a), b), d) and e) in each case preferably over the entire length from the central lens to the outer edge of the aperture opening.

Preferably, the layers of the further suspension elements are also each integral with the corresponding layers of the central lens and the first Suspension element formed.

In other words, the five layers a) to e) of the lens and the five layers a) to e) of the first suspension element are formed integrally in pairs at least to the outer frame of the aperture diaphragm.

Due to the production according to the invention, however, the thicknesses of the layers a) to c) are already sufficiently large in the region of the suspension elements alone to suspend the electrode belonging to the central lens and the associated electrode support region in the aperture opening in a self-supporting manner. Particularly preferably, the thickness of the original membrane in the region of the suspension elements alone is already sufficiently large to suspend the electrode belonging to the central lens in the aperture opening in a self-supporting manner and / or to produce the lens opening in a self-supporting state.

In the following the invention is based on

Embodiments and with reference to the figures explained in more detail, wherein the same and similar elements are partially provided with the same reference numerals and the features of various embodiments can be combined.

Brief description of the figures

1 is a schematic cross-sectional view of a

Phase-contrast TEMs with phase plate,

2 is an electron micrograph of a silicon chip with two silicon nitride membrane windows, Fig. 3 is a schematic plan view of a

Multi-membrane chip and two cuts along lines A and B,

4 to 10 show schematic cross-sectional views of the production according to the invention of a Boersch

Phase plate,

11 is an electron micrograph of a section of the membrane after application and structuring of the electrode layer according to the method step shown in Fig. 6,

FIG. 12 is a schematic plan view of a chip with a membrane and a Boersch phase plate with an enlarged detail. FIG. 13 is a schematic plan view of a chip with a membrane and a Boersch phase plate with an enlarged detail C, wherein the layers 60 and 70 are made invisible,

Fig. 14 is a schematic sectional perspective view of the lens of an inventively prepared Boersch phase plate with three suspension elements and

Fig. 15 is a schematic cross-sectional view of a solid lens assembly made according to the invention.

Detailed description of the invention

Fig. 1 shows a transmission electron microscope 1 with a phase plate 20 as described in the introduction.

Important for the feasibility of subsequent structuring steps in the course of the present invention is a flat base for the construction of a layer arrangement. This can be metallic or insulating. The thickness of the pad significantly influences the entire thickness of the lens assembly to be produced. In the context of the invention therefore very thin membranes are used as a base. The membrane becomes part of the lens arrangement to be produced. With this, overall thicknesses of the lens arrangement of a few 100 nm can be realized.

Referring to FIG. 2, for the embodiment described below, an approximately 100 nm thin silicon-nitride layer enriched in silicon deposited on a silicon wafer is used, which forms a self-supporting silicon nitride membrane 30 in two membrane windows 34. This has proven to be particularly suitable, especially since silicon nitride is an excellent insulator.

The membrane or film 30 is held by a handleable stable, that is considerably thicker and larger frame-like chip 32 and is mounted in Fig. 2 on the underside of the chip 32 and forms there a flat surface. The chip 32 may comprise a single membrane window 34 with a membrane 30, but there may also be two (Figure 2) or more (Figure 3) membrane windows 34, i. a plurality of membranes 30 may be held or clamped in the wafer.

Step a)

In the preferred example herein, the insulating silicon nitride membrane 30 within the membrane window 34 has a thickness d _m of about 100 nm. Referring to FIG. 4, in a first step, the chip 32 is provided with the membrane 30 deposited on a flat front side 32a (in FIGS. 4 to 10 above). The silicon nitride layer 31, which forms the membrane 30, has a cantilevered area within the membrane 30 Window 34 and an integrally formed with the cantilevered area or the membrane 30 edge portion 31 a, which is connected in a flat with the outer frame portion 33 of the chip 32. In other words, at least one of the layers is thus produced from a self-supporting membrane 30 which extends up to the frame region 33 of the chip 32. The window 34 is etched into the latter from the back side 32b (in FIGS. 4 to 10 below) of the chip 32, up to the membrane 30, so that the window 34 has a recess on the back side up to the membrane 30 in FIG

Chip 32 defined. The chip 32 with the silicon nitride membrane 30 used was purchased from Silson (www.silson.com). This silicon nitride membrane 30 advantageously has a sufficiently smooth surface on its front side 30a in order to spin up corresponding lithographic coatings in later steps.

The dotted box 34 represents the area of the phase plate to be made and the smaller dotted box 36 the area of the central lens 90 which will later be cantilevered in the aperture opening. The silicon nitride membrane 30 remains as one of the two insulating layers of the phase plate 20. The cross-sectional drawings are not to scale.

Step b)

In the next step, shown in FIG. 5, the underside 30b of the membrane 30 is metallized with a suitable metal layer 40. In the exemplary embodiment, for this purpose, the rear side 30b of the silicon nitride membrane 30 is vapor-deposited with a gold layer 40 having a thickness d _a i of about 200 nm.

Step c) Referring to FIG. 6, the electrode 52 and lead 54 are defined on the front side 30a of the membrane 30. For this purpose, the insulating side of the two-layer arrangement of the layers 30 and 40 (here front 30 a of the membrane 30) with a photo or electron beam sensitive lacquer is lacquered (not shown). On this varnish, the supply lines and the electrode or electrodes, which are to define the lens later, are exposed optically or electron beam lithographically. In this case, a plurality of exposure steps and / or coating steps can be carried out. The location at which the respective exposure is to take place is given by knowing the position of the membrane 30 or membranes 30 within the chip 32 with sub-μ accuracy either in advance or determined before the exposure. Both optically and under an electron microscope, the membranes 30 provide sufficient contrast to locate them. When locating by means of the electron microscope and in the presence of an electron beam-sensitive paint care is taken that the exposure threshold dose of the paint used is not exceeded. After the exposure and development of the paint, the front of the sample is metallized and then the lift-off is performed to produce the electrode 52 and the lead 54. In this case, a metal layer 50 is vapor-deposited, which extends up to the chip 32 in order to be able to subsequently contact the supply line 54 at a contacting field 58. In particular, in the same step, position markings 56, in this example three, preferably around the electrode 52, are defined in order to be able to position the diaphragm 30 accurately later (see FIG. 11). The sample may also be re-lacquered and subjected to a further patterning step to define further leads and / or electrodes. The position markings 56, so-called alignment marks, as well as the circular approximately 2 .mu.m diameter circular electrode 52 and the approximately 1 .mu.m wide feed line 54 can best be seen in the SEM image of FIG. The structuring can be carried out both optically and electron beam lithographically, whereby mixing methods were successfully used.

The choice of the lithographic process is an essential criterion for the minimum achievable dimensions of the structures and thus the phase plate. Coarse structures such as the contacting screens 58 are efficiently produced by photolithography. In the present example, the electrode 52, the immediately adjacent

Section of the lead 54 and the position marks 56 produced by electron beam lithography. Hereby, dimensions for the leads 54 and electrodes 52 down to 30 nm width could already be achieved experimentally. It is also possible to produce even finer electrodes 52 with the aid of an atomic force microscope. With the methods mentioned, the dimensions, arrangement and shape of the electrodes can be varied so that not only rotationally symmetrical but also field distributions with more complex symmetries can be realized. Thus, aspheric lenses can be made with, for example, quadrupole, octupole or hexapole symmetry.

To produce the electrode 52, the feed line 54 and the position marking 56, a gold layer was likewise vapor-deposited as the electrode layer 50 in the exemplary embodiment. In principle, however, other metals are also suitable. The thickness d _{e of} the electrode was chosen according to the embodiment between 50 nm and 200 nm. However, thinner and thicker electrodes and leads between about 10 nm and a few microns are possible.

Step g) Referring to Fig. 7, after application and

Structuring the electrode layer 50 with the electrode 52 and feed line 54, the aperture 36 is made around the electrode 52. According to the invention, a so-called focused ion beam device ("Focus Ion Beam Device") is used.The device is available from the company Zeiss.This device is by means of an ion beam, for example, 30 kV gallium ions, the material in the range the aperture opening 36 is milled around the electrode 52 and leaving recesses 38, in this example a number of three, defining the general internal shape of the aperture 36 of the phase plate 20 (see Fig. 12) the material of the silicon nitride membrane 30 and the lower gold layer 40 are sputtered away, that is, it is not lithographed and no varnish is needed, and the focused ion beam can also be used for imaging to position the membrane 30. Further, the focused used Ion beam device can also be imaged via an additional scanning electron microscope column, which has been incorporated herein by reference en method also used.

As can be seen in FIG. 12, the step of milling out results in a base mold for a cantilevered lens construction with a support region 39 of the membrane suspended from the connecting webs 38 around the electrode 52. Positioning with an accuracy in the range of achieved about 100 nm. In this step g), therefore, the shape of the aperture opening 36, the connecting webs 38 and the carrier region 39 is generated around the electrode 52. However, in this step, the lens bore 80 is not yet manufactured.

Step d)

Referring to Fig. 8, as a next step, a second insulating layer 60 is evaporated on the front side of the sample by electron beam assisted PVD.

The second insulating layer 60 completely covers the electrode 52 and an inner region or connecting section 55 of the feed line 54 in order to insulate the feed line 54 and the electrode 52. Only that

Contact pad 58, so-called contact pad, is shaded and not isolated. At the contact pad 58, the electrical connection of the electrode 52 is later made possible via the feed line 54 with macroscopic feed lines 96, for example contact pins or wires. However, it is also conceivable to apply the second insulation layer 60 prior to milling out the aperture opening 36. In the exemplary embodiment, aluminum oxide having a thickness di ₂ of approximately 200 nm has particularly preferably proved to be the second insulating layer 60.

Steps)

Referring to Fig. 9, a second shielding layer 70, in this example a

Metal layer, more precisely about 200 nm (d _a 2) thick gold layer applied, more precisely vapor-deposited. Preferably, an approximately 5 nm thick chromium adhesive layer is vapor-deposited under the metal layers a), c) and e). In the present example for producing the cantilevered phase plate 20 with aperture 36 and the structures therein, the chip 32 is incorporated into the metallization unit so that there is an angle between the chip normal 94 and the propagation direction of the metal vapor upon deposition. In addition, during coating or metallization, the chip 32 is tilted and / or rotated in several different directions. It is thereby achieved that the central lens 90 and the connecting plates 38 of the phase plate are also laterally vaporized with metal and thus completely enclosed with metal, so that the electric field is completely shielded when a voltage is applied to the supply line 54 and electrode 52. For this purpose, during operation, the shielding or Faraday cage formed by first and second shielding layers 40, 70 is earthed.

The experiments carried out have shown that the material for the two insulating layers 30, 60 and the two shielding layers 40, 70 can be varied in many ways. The thicknesses of the layers can vary between 10 nm and a few microns. The layer thickness of the two insulation layers 30, 60 is selected to be sufficiently thick in order, in accordance with the respective insulation material, not to exceed the breakdown voltage during operation of the lens.

Step f) Referring to Fig. 10, by means of the focussed

Ion beam device, the central lens aperture 80 through the entire layer package - the five layers a) to e) including the lens electrode 52 - milled or cut. This results in the ring shape of the lens electrode 52. The milling takes place here by local sputtering of the material. The diameter of the opening thus created is about 1 micron in the embodiment.

By means of sputtering milling with the focussed

Ion beam device can be ensured that no electrical short circuits between the different metal layers 40, 50 and 70 arise. The preferred method sequence f) according to e) according to {d) and g)} and the tilting, ensures that the

Connecting webs 38 and the area around the ring electrode 52 are completely covered from the outside with the metal layer 70, but not the inner periphery of the bore 80, where the three metal layers 40, 50, 70 from the two insulating layers 30, 60 against each other. As can be seen in FIG. 10, the five layers 30, 40, 50, 60 and 70 are exposed to the outer circumference of the bore 80.

Finally, the contacting field 58 is contacted by means of a macroscopic contact element 96.

The phase plate produced according to the invention was tested for break-through resistance and has a breakdown voltage greater than 2.5V. This is sufficient for operation as a Boersch phase plate in a TEM. The typical operating voltage is in the range of 1 V.

Fig. 13 shows a possible design of the Boersch phase plate. In the illustration, the layers 60 and 70 of the finished phase plate are made invisible to visualize the electrode. The phase plate, as shown in Fig. 13, comprises an annular lens 90 with embedded ring electrode 52. The central lens 90 has an approximately 1 micron diameter bore 80, through which the zero beam 10 of the TEM 1 is guided. The central lens 90 is suspended in the aperture opening 36 in a self-supporting manner via three suspension elements 92, of which the connecting webs 38 are part. During operation of the lens 90, an electric field prevails substantially in the area of the bore 80, but not in the region of the aperture 36, through which the scattered electrons are passed.

The Boersch phase plate with its aperture opening 36 and frame-like aperture stop 37 is in the frame-like support chip 32, which has a significantly greater thickness D of 200 microns in this example, that is about 1000 times thicker than the membrane 30 and at least 100 times thicker as the total thickness of the phase plate 20 is clamped. The feed line comprises the connection section 55 and an outer, wider line section 55a, which extends from the window 34 enlarged in section C to the frame region of the chip 32, in order to open in the contacting field 58. So it will be the

Layers 40, 50, 60, 70 applied in steps b) to e) on the self-supporting membrane 30, which spans the membrane window 34.

14 shows the layer structure of the insulating sheath and shield support members 92 and within the bore 80 of the central ring lens 90. It will be best appreciated that the lateral end faces 91, 93 of the central ring lens 90 and suspension members 92 are electrically conductive

Material of the second shielding layer 70 are coated. The advantages of a Boersch phase plate compared to a Zernicke phase plate when used in a TEM are as follows:

The fact that the Boersch phase plate is enclosed by a metal layer, it withstands direct irradiation by the electrons for a long time.

By applying various potentials to the ring electrode, the strength of the electric field and thus the phase shift of the zero beam can be adjusted continuously without removing the phase plate.

The interaction between the image-forming electrons with the phase plate is low, in contrast to the Zernicke phase plate, so that coherence and signal losses are significantly reduced.

In addition, the phase shift between non-scattered and scattered electrons is spatially constant, and therefore not subject to local variations as in the case of the granular carbon layer in the Zernicke phase plate.

In the foregoing, the production of a Boersch phase plate 20 with cantilevered lens 90 on suspension elements 92 has been described by way of example. However, it is obvious to the person skilled in the art that the method according to the invention can also be used for producing surface-closed electrodes or electrodes in a wide variety of forms. This eliminates the step of milling out the aperture opening (step g)) and the arrangement need not be tilted when applying the second metallization layer 70. An example of a cross section through such a flat solid lens arrangement 100 without aperture opening is shown in FIG. 15.

In summary, a production method for electrostatic micro or nano-lenses is proposed, by means of which a reduction of the lens size to less than 1 μ is possible. By selecting a suitable substrate and combination of lithography and

Nanostructuring techniques can achieve great variability in lens dimensions, field strengths, and field distributions. With the method according to the invention not only massive multilayer micro or nano-lenses, but - according to the best of the inventors for the first time - even a functioning Boersch phase plate, that is, a cantilevered lens construction actually be realized.

Claims

claims

A method of manufacturing a phase plate (20) for incorporation in an electron microscope (1), comprising the steps of:

Providing a handleable stable chip (32), the chip (32) having at least one thin self-supporting membrane (30) disposed in a membrane window (34) of the chip defining a planar front face (30a) of the chip;

Membrane in the form of a first insulating layer remains as part of the phase plate (20) to be produced,

Applying an electrically conductive first shielding layer (40) on a front side (30b) of the membrane opposite the front side,

Producing an electrode (52) and a feed line (54) of electrically conductive material on the front side of the membrane (30a),

Milling an aperture opening (36) from the membrane (30) with the recess of a

Electrode carrier region (39) and at least one connecting web (38) as part of a suspension element (92) to be produced, the electrode carrier region (39) being suspended from the connecting web (38),

Applying an electrically insulating second insulation layer (60) to the electrode support region (39) and the suspension element (92) such that the electrode (52) and at least partially the lead (54) are covered by the second insulation layer (60) (52) and at least partially enclosing the lead (54) between the first and second insulating layers (30, 60), applying an electrically conductive second A shielding layer (70) on the opposite side of the electrode of the second insulating layer (60), wherein the phase plate (20) is tilted and / or rotated to the lateral end faces (91, 93) of the electrode carrier region (39) and at least partially of the suspension element ( 92) with the electrically conductive material of the second shielding layer, wherein electrical contact is made between the first and second shielding layers (40, 70), whereby the first and second shielding layers form a closed electrical shielding cage around the electrode (52) and at least partially forming the lead (54) and the shielding cage is electrically isolated from the electrode (52) by means of the first and second insulation layers (30, 60), thereafter piercing the phase plate (20) in the region of the electrode (52) the inner opening (80) is produced in the electrode with a diameter between 1 nm and 100 μm, so that the

Ring shape of the electrode (52) is formed and the layers of the lens assembly to the bore (80) are exposed towards.

Phase plate (20) with frame-like support chip

(32), in particular for installation in a focal plane of an electron microscope lens (9), wherein the phase plate (20) has a frame-like aperture stop (37) which defines an aperture (36) for scattered electrons (16) in the electron microscope and within the Aperturöffnung (36) an electric lens (90) for phase shifting the null beam (10) when passing through the lens (90) is provided, wherein at least a first suspension element (92) the aperture (36) spans and the lens (90) is suspended at least by the first suspension element (92) on the aperture (37), the phase plate (20) at least in the region of the lens (90) at least five layers a) to e a) a first electrically conductive shielding layer (40), b) a first insulating layer of electrically insulating material (30), c) an electrically conductive structured electrode layer (50) with an electrode (52) belonging to the lens and a Lead (54), d) a second insulating layer (60) of electrically insulating material, e) a second electrically conductive shielding layer (70), the lens (90) having a bore (80) defining a continuous channel through the layers of the Lens (90) is formed so that the electrode (52) is formed as a ring electrode around the bore (80) around, by applying an electric potential to the electrode (52) the electrical Lens array (12) to produce and wherein the phase plate (20) in a window (34) of the chip (32) is suspended.

3. phase plate (20) according to claim 2, wherein at least one of the layers a), b), d) or e) extends to the frame region (33) of the chip (32).

4. phase plate (20) according to claim 3, wherein the one layer in the membrane window (34) arranged and self-supporting membrane (30) and integrally formed with the membrane edge region (31 a), which extends flat on the frame region (33) of the chip.

5. phase plate (20) according to claim 3 or 4, wherein the thickness of a layer in the region of

Suspension element (92) alone is already dimensioned sufficiently large to suspend the electrode (52) belonging to the central lens (90) in the aperture (36).

6. phase plate (20) according to any one of claims 3 to 5, wherein the one layer is the first insulating layer.

7. phase plate (20) according to any one of the preceding claims, wherein the first insulating layer is a silicon nitride layer.

8. phase plate (20) according to any one of the preceding claims, wherein the first insulating layer has a thickness between 1 nm and 5 microns.

A phase plate (20) according to any one of the preceding claims, wherein the lead (54) is integral with the ring electrode (52) and extends along the suspension member (92) from the ring electrode (52) to the chip (32). to be able to apply an electrical potential to the electrode (52) from the outside.

10. phase plate (20) according to any one of the preceding claims, wherein the feed line (54) has an elongated

Connecting portion (55) which extends radially on the first connecting web (38) from the ring electrode (52) to the chip (32) and comprises a contact area (58) adjoining the connecting portion (55) on the chip (32) , around to be able to apply a voltage to the ring electrode by means of a voltage source connected to the contacting field (58), and wherein the ring electrode (52), the connecting portion (55) and the contacting field (58) are integrally formed.

11. phase plate (20) according to any one of the preceding claims, wherein the phase plate (20) arranged a plurality of star-like around the lens and the aperture opening (36) radially spanning

Suspension elements (92) by means of which the lens in the aperture opening (36) on the aperture stop (37) is suspended.

The phase plate (20) of claim 11, wherein the further suspension members (92) are sandwiched and comprise at least the four layers a), b), d) and e).

13. phase plate (20) according to claim 11 or 12, wherein the

Layers of the further suspension members (92) are each integrally formed with the respective layers of the central lens and the first suspension member (92).

14 phase plate (20) according to any one of claims 11 to 13, wherein the thicknesses of the layers a) to c) in the region of the suspension elements alone are already dimensioned sufficiently large to the lens belonging to the electrode (52) in the aperture (36). hang.

15. phase plate (20) according to any one of the preceding claims, wherein the first and second insulating layer

(30, 60) together an outwardly closed electrically insulating sheath around the ring electrode (52) and the feed line (54), the casing extending annularly around the ring electrode (52) and extending at least to the outer edge of the aperture (36).

16. The phase plate (20) of claim 15, wherein the first and second shield layers (40, 70) together form an electrically conductive cage closed to the outside around the electrically insulating sheath, the conductive cage extending annularly around the sheath and extending at least as far as extends the outer edge of the aperture (36).

The phase plate (20) of any of the preceding claims, wherein the first suspension member (92) is sandwiched over its entire length from the lens (90) to the outer edge of the aperture (36) from the five layers a) to e) ,

18. phase plate (20) according to one of the preceding

Claims, wherein the five layers a) to e) of the lens (90) and the five layers a) to e) of the first suspension element (92) at least to the outer edge of the aperture (36) are each formed integrally in pairs.

19. A phase-contrast transmission electron microscope (1), comprising: an electron source (2) for irradiating a sample (8) with an electron beam (4) in the through-light method, an imaging lens system, the phase plate (20) according to one of the preceding claims 2 to 18, arranged in the rear focal plane of an electron microscope lens (9) and an image pickup device (24) for picking up an enlarged image of the sample behind the phase plate (20).

A method of making a multilayer electrostatic lens assembly (20, 100) having at least one lens electrode (52) electrically shielded on both sides by shielding layers (30, 60) to create an electric field in an inner aperture (80) of the lens electrode comprising the steps of: a) providing a chip (32) which has at least one membrane window (34) with a membrane (30) of a first membrane material, wherein the membrane (30) comprises a first layer (31) of the lens arrangement to be produced ( 20, 100), b) applying a second layer (40) of a coating material on a first side (30b) of the membrane (30), wherein either the membrane material is an electrically insulating material and the coating material is an electrically conductive material or the membrane material electrically conductive material and the coating material are an electrically insulating material, so that anindes t two-layered membrane (30, 40) of an electrically insulating first insulating layer and an electrically conductive first shielding layer (40) is formed, c) generating an electrode (52) and a feed line (54) of electrically conductive material on the electrically insulating layer of the membrane (30), d) applying an electrically insulating second insulation layer (60) at least on the electrode (52) and the lead (54), e) applying an electrically conductive second shielding layer (70) on the second insulating layer (60), so that in the membrane window (34), a sandwich-like layer arrangement is formed, which comprises at least the following five layers in the region of the electrode: the first

Shielding layer, the first insulating layer, the electrode, the second insulating layer and the second shielding layer, f) drilling through the layer arrangement in the region of the electrode (52), wherein the inner opening (80) is produced in the electrode (52).

21. The method of claim 20, wherein as the membrane (30) of the chip (32) in step a) a silicon nitride membrane is used.

22. The method according to claim 20 or 21, wherein the membrane

(30) has a thickness of between 1 nm and 5 μm.

23. The method according to any one of the preceding claims, wherein the piercing of the layer assembly by means of micro- or nano-milling is performed.

24. The method according to any one of the preceding claims, wherein the piercing of the layer arrangement is performed by means of a focused ion beam.

25. The method according to claim 1, wherein the step c) comprises: structuring an electrically conductive electrode layer (50) applied to the electrically insulating layer of the membrane by means of photo or electron beam lithography with spin-coating and lift-off technology, wherein the Shape of the electrode (52) and a substantially elongated shape of the feed line (54) are generated.

26. Method according to one of the preceding claims, wherein the lens arrangement is produced in the form of a phase plate (20) for an electron microscope (1), wherein the phase plate (20) has a frame-like aperture stop (37) which has an inner aperture opening (36) for Scattered electrons (16) defined in the electron microscope, wherein within the aperture opening a lens electrode (52) by means of at least one

Suspension element (92) is suspended on the aperture diaphragm (37), wherein the membrane (30) has at least the size of the aperture diaphragm (37) and in a step g) subsequently at least the

Step a), the aperture (36) is generated, wherein of the membrane (30) an electrode support area around the electrode (52) and at least a first connecting web (38) remain such that the electrode support region (39) by means of the first

Connecting web (38) on the aperture (37) inside the aperture (36) is suspended.

27. The method according to claim 26, wherein in step g) the aperture opening (36) with the recess of the

Electrode support portion (39) and the at least one connecting web (38) from the membrane (30) is milled.

28. The method of claim 27, wherein the milling is performed by means of a focused ion beam.

29. The method according to any one of claims 26 to 28, wherein prior to generating the aperture opening (36) a plurality of Position markers (56) for positioning the assembly for the step g) is generated.

30. The method according to any one of claims 26 to 29, wherein in step g) a plurality of star around the

Electrode support region arranged connecting webs (38) remain, by means of which the electrode carrier region (39) is suspended from the aperture (37).

31. The method according to any one of claims 26 to 30, wherein in step b), the second layer is applied at least over the entire surface of the aperture stop (37).

32. The method according to any one of claims 26 to 31, wherein in step c) the supply line (54) as extending from the electrode (52) to at least on a membrane window (34) framing frame portion (33) of the chip (32) extending becomes.

33. The method according to claim 26, wherein the feed line extends on the first connecting web, the connecting web has a greater width than the feed line and the electrode carrier region has a larger diameter than the electrode. 52) and the lead (54) and the electrode (52) are framed in a plan view of the substrate material.

34. The method according to any one of claims 26 to 33, wherein the application of the second insulating layer (60) according to step d) after the generation of the aperture opening (36) according to step g) is performed.

35. The method according to any one of claims 26 to 34, wherein the steps d) to g) are carried out in the following order:

Producing the aperture opening (36) according to step g), subsequently applying the second one

Insulating layer (60) according to step d), subsequently applying the second shielding layer (70) on the second insulating layer (60) according to step e), subsequently piercing the layers of the produced phase plate (20) according to step f).

36. The method according to any one of claims 26 to 35, wherein the phase plate (20) during application of the second shielding layer (70) is tilted and / or rotated to the lateral end faces (91) at least the electrode carrier region (39) with the electrically conductive material the second shielding layer (70), wherein an electrical contact between the first and second shielding layer

(40, 70), whereby the first and second shielding layers form a closed electrical shielding cage around the electrode (52) and the shielding cage is electrically isolated from the electrode (52) by means of the first and second insulating layers (30, 60). is isolated.

37. Multilayer lens arrangement (20, 100), producible by the method according to one of the preceding claims.